---
name: "CPS::Governor"
section: "3pm"
platform: "linux"
package: "libcps-perl"
version: "0.19-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/CPS::Governor"
---

# CPS::Governor(3pm)

control the iteration of the "CPS" functions

## NAME

"CPS::Governor" - control the iteration of the "CPS" functions

## DESCRIPTION

Objects based on this abstract class are used by the `"gk*"` variants of the CPS functions, to control their behavior. These objects are expected to provide a method, `"again"`, which the functions will use to re-invoke iterations of loops, and so on. By providing a different implementation of this method, governor objects can provide such behaviours as rate-limiting, asynchronisation or parallelism, and integration with event-based IO frameworks.

## CONSTRUCTOR

### $gov = CPS::Governor-\>new

Must be called on a subclass which implements the `"again"` method. Returns a new instance of a governor object in that class.

## SUBCLASS METHODS

Because this is an abstract class, instances of it can only be constructed on a subclass which implements the following methods:

### $gov-\>again( $code, @args )

Execute the function given in the `"CODE"` reference `$code`, passing in the arguments `@args`. If this is going to be executed immediately, it should be invoked using a tail-call directly by the `"again"` method, so that the stack does not grow arbitrarily. This can be achieved by, for example:

```
 @_ = @args;
 goto &$code;
```

Alternatively, the Sub::Call::Tail may be used to apply syntactic sugar, allowing you to write instead:

```
 use Sub::Call::Tail;
 ...
 tail $code->( @args );
```

## EXAMPLES

### A Governor With A Time Delay

Consider the following subclass, which implements a `"CPS::Governor"` subclass that calls `"sleep()"` between every invocation.

```
 package Governor::Sleep
 use base qw( CPS::Governor );
 sub new
 {
    my $class = shift;
    my ( $delay ) = @_;
    my $self = $class->SUPER::new;
    $self->{delay} = $delay;
    return $self;
 }
 sub again
 {
    my $self = shift;
    my $code = shift;
    sleep $self->{delay};
    # @args are still in @_
    goto &$code;
 }
```

## SEE ALSO

- •

  Sub::Call::Tail - Tail calls for subroutines and methods

## AUTHOR

Paul Evans \<leonerd@leonerd.org.uk\>